Reception automatic gain control system and method

• US 5,784,410 A
• Filed: 06/03/1996
• Issued: 07/21/1998
• Est. Priority Date: 06/03/1996
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nakano, Takayuki
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US08/657,090
• Time in Patent Office: 778 Days
• Field of Search: 375/345, 330/278, 330/254, 455/234.1, 455/245.1, 455/232.1, 348/678, 348/685
• US Class Current: 375/345
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence

Abstract

An automatic gain control system is disclosed which incorporates a control error amplitude limiting circuit to provide fine gain control for relatively small control error values, while providing limited gain renewal values to maintain amplifier stability for relatively large control error values. In another embodiment, an automatic gain control system is disclosed which incorporates a variable scaling means which scales the control error with coefficients selected in accordance with the positive or negative sign of the control error to provide maximum control loop response rates which are the same for both increases and decreases in signal power. Automatic gain control systems and methods are disclosed which respectively limit the control error amplitude and scale the control error with coefficients selected on the basis of the cotnrol error being either positive or negative, to provide improved, more precise, and more symmetrical amplifier gain control.

Claims

1. An automatic gain control system responsive to gain renewal values generated therein, comprising:

control error detecting means for providing control error signals; and

amplitude limiting means coupled directly to said control error detecting means for amplitude limiting said control error signals;

scaling means coupled to said amplitude limiting means to scale the output therefrom and generate said gain renewal values,

said amplitude limiting means and said scaling means acting to reduce asymmetric control loop response of said automatic gain control system.

2. The automatic gain control system of claim 1 wherein said scaling means provides a fixed scaling factor.

3. The automatic gain control system of claim 1 wherein said scaling means provides variable scaling factors having values dependent on the sign of said control error signals.

4. The automatic gain control system of claim 1 wherein said amplitude limiting means provides a variable magnitude output when said control error signals lie within a predetermined range of magnitudes and a constant magnitude output when said control error signals exceed said predetermined range.

5. The automatic gain control system of claim 1 wherein said control error signals are linear with respect to power of a signal input to said automatic gain control system.

6. An automatic gain control system responsive to gain renewal values generated therein, comprising:

control error detecting means for providing control error signals; and

variable scaling means coupled to said control error detection means for variably scaling said control error signals in accordance with the sign of said control error signals to generate said gain renewal values, said variable scaling means acting to reduce asymmetric control loop response of said automatic gain control system.

7. The automatic gain control system of claim 6 further including a linear to logarithmic converter coupled to the input of said control error detecting means.

8. The automatic gain control system of claim 6 further including a linear to logarithmic converter coupled between said control error detecting means and said variable scaling means.

18. The automatic gain control system of claim 6 further including amplitude limiting means for providing amplitude limited control errors to said variable scaling means.

19. The automatic gain control system of claim 6 wherein said variable scaling means generates gain renewal values which are substantially the same for positive and negative control error signals of the same magnitude.

9. A method for generating gain renewal values to control the gain of an automatic gain control system comprising the steps of:

generating control error signals;

amplitude limiting said control error signals to generate amplitude-limited control signals; and

scaling said amplitude-limited control signals to generate gain renewal values which reduce asymmetric control loop response of said automatic gain control system.

10. The method of claim 9 wherein said step of scaling provides fixed scaling of said amplitude-limited control signals.

11. The method of claim 9 wherein said step of scaling provides variable scaling of said amplitude-limited control signals in accordance with the sign of said control error signals.

12. A method for generating gain renewal values for controlling the gain of an automatic gain control system comprising the steps of:

generating control error signals which are linear with respect to the detected power of a signal input to said automatic gain control system;

converting said control error signals to logarithmic error signals; and

variably scaling said logarithmic error signals to generate gain renewal values which reduce asymmetric control loop response of said automatic gain control system.

13. A method for generating gain renewal values for controlling an automatic gain control system, comprising the steps of;

generating control error signals which are logarithmic with respect to power of a signal input to said automatic gain control system; and

variably scaling said control error signals by factors selected in accordance with the sign of said control error signals, said factors selected to reduce asymmetric control loop response of said automatic gain control system.

14. An automatic gain control system comprising:

a variable gain amplifier for receiving and amplifying a communication signal in accordance with gain control values input thereto;

analog to digital converter means for converting said amplified communication signal to digital form;

power calculation means for calculating the power of said digitally converted communication signal;

control error detecting means for generating control error signals representing a deviation of said calculated power from a predetermined reference; and

processing means responsive to said control error signals for generating gain renewal values by scaling said control error signals with scale factors depending upon the sign of said control error signals selected to reduce asymmetric control loop response of said automatic gain control system, said gain renewal values being used to adjust said gain control values input to said variable gain amplifier.

15. The automatic gain control system of claim 14 wherein said processing means scales said control error signals with variable scale factors.

16. The automatic gain control system of claim 14 wherein said processing means further comprises amplitude limiting means for amplitude limiting said control error signals.

17. The automatic gain control system of claim 16 wherein said processing means scales said control error signals with variable scale factors.